.selected { color: red; }

.center{
  text-align: center;
}

.mp{
  margin: 20px;
  padding: 10px;
}

a {
  color: blue;
}
/* 未被访问的链接 */
a:visited {
  color: #21dc15;
  font-family: Arial;
  color: gray;
}

a:hover {
  color: #0f57c5;
  text-transform: uppercase;
}

/* 鼠标指针移动到链接上 */
a:active {
  color: #d20e94;
}
